Fruits: For newly planted strawberries, pinch off any flowers or developing fruits to encourage the plants to develop strong root systems instead of putting energy into producing fruits. You can start harvesting the following season.
Monitor apple trees for apple maggot adult populations and other fruit insects using yellow sticky cards, pheromone traps and red sticky balls. Put up traps, cards and sticky balls right after petal fall. Check DATCP’s free electronic publication The Wisconsin Pest Bulletin (http://datcpservices.wisconsin.gov/pb/) on a weekly basis to check on local pest populations. This will help you stay ahead of the pests.
An organic insect repellent spray that can be used on apple trees is called “Surround” and it contains kaolin clay. It needs to be re-applied several times during the season, and it should not be applied within three weeks of harvest. Make sure to wash all the residue off the fruit.
Shrubs: Prune spring-flowering shrubs such as lilacs, forsythia, mock orange, Korean-spice viburnum, bridal-veil spirea and weigela within two to three weeks after they flower. After this time they begin forming new flower buds for next year, so you don’t want to prune too late and remove flower buds for next year.
Vegetables: Green beans can be planted in successive plantings starting at the end of May and beginning of June to extend the season. Cucurbits such as melons, winter and summer squash, cucumbers and okra can be planted safely after the first week in June. Soil temperatures around 80 degrees are actually optimal for germination of these crops, so planting earlier when the soil is too cold does not help you get ahead. Often the crops will fail to germinate or become stunted.
Watch for the spotted and the striped cucumber beetle on cucurbits. Both beetles are yellowish-green and small — about one-quarter inch long. As you might guess, the striped beetle has stripes and the spotted one has spots. The striped species tends to be the one that causes the most damage in Wisconsin. They are important because both can transmit bacterial wilt, a lethal disease of cucurbits, when they feed on melons and cucumbers. They also feed on squash and pumpkins, but don’t transmit the disease to these crops. If populations are high enough, chemical control may be needed. You can use floating row cover to protect the crops early in their development before they start to bloom. Once they bloom, of course, you need to remove the cover so the pollinators can do their work. For more information on the cucumber beetles, visit https://learningstore.uwex.edu/ and enter “cucumber beetles” in the search box.